Girth weld coater

ABSTRACT

A girth weld coating machine has an application head rotatable about a pipeline. A reservoir of coating material is carried on the application head and progressively dispenses coating material on to the girth weld. The coating material is applied to the pipe surface by a roller to spread and distribute the coating over the surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/897,527 filed on Feb. 15, 2018 and claims priority to U.S.Provisional Patent Application No. 62/460,236 filed on Feb. 17, 2017,the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a machine to apply a coating to a girthweld of a pipeline.

DESCRIPTION OF THE PRIOR ART

A pipeline is formed from sections of pipe arranged end to end. Thesections are welded to one another about their circumference to providea continuous fluid tight seal. The weld between adjacent sections isreferred to as the girth weld. The exterior surface of sections of pipeis coated during manufacture for corrosion resistance, but the ends ofthe sections must be left uncoated to allow the girth weld to beperformed. Once the weld is formed, it is necessary to coat the exposedends of each section of pipe to at least the same standard as the restof the pipe to form a continuous impervious outer coating.

Whilst manual coating of the girth weld is possible, the size andfrequency of the girth welds makes this impractical. Moreover, theconsistency of manual coating does not meet the quality standards forthe coating unless great care is taken.

It is common practice to spray a coating on the girth weld using a twopart epoxy coating. The spraying may be performed with a machine used toapply a coating to an entire section of pipe after it has been cleanedof previous coating. Such a machine is shown in FIGS. 1 to 12 of PCTapplication PCT/CA2012/050027, published as WO2012/094767, the contentsof which are incorporated herein by reference.

This machine is intended to progress along a pipe as a spray headoscillates to apply a coating. Whilst this machine is effective inapplying a coating on a continuous basis, it is not as satisfactorywhere intermittent stationary operation is required, such as in coatinga girth weld. This is because the coating necessarily has a limited worktime and therefore it is necessary to clean the spray head after eachapplication before the machine can be repositioned and set up on thenext girth weld. Cleaning requires the use of a solvent, whichintroduces volatiles in to the environment and therefore is generallyundesirable.

WO 2012/094767 also shows in FIGS. 18 to 25 a girth weld coating machinethat is mounted on the pipeline over a girth weld. It dispenses acoating on to the girth weld and spreads the coating as the machinerotates. The coating is dispensed from a reservoir provided by a pair ofcartridges, one for each component of the coating, and a spreader in theform of a blade spreads the coating over the surface of the pipesections. The cartridges are sized to contain enough coating for onegirth weld and are disposable so they may be removed after eachapplication.

This arrangement has proved satisfactory in applying a coating to thegirth welds and avoids the necessity of cleaning the dispensingapparatus with solvents after each application. However, variations inthe consistency of the coating and the ambient conditions necessitatecareful adjustment of the machine if a coating of the requisite qualityis to be obtained.

It is therefore an object of the present invention to obviate ormitigate the above disadvantages.

SUMMARY OF THE INVENTION

In general terms, the present invention provides a girth weld coatingmachine having an application head rotatable about a pipeline. Areservoir of coating material is carried on the application head andprogressively dispenses coating material on to the girth weld. Thecoating material is applied to the pipe surface by a roller to spreadand distribute the coating over the surface.

Preferably, the roller is driven and is interposed between the outlet ofthe reservoir and the surface of the pipe.

As a further preference, the roller is forced toward the surface of thepipe during distribution of the coating and the force applied ismodulated during application.

As a still further preference, the roller is lifted from the surface ofthe pipe while the roller is driven and continues to rotate.

In a preferred embodiment, the reservoir has a bag to contain thecoating with an elongate nozzle arrange parallel to the axis of rotationof the roller. The bag is supported on a platen and coating material isforced from the bag by a roller moving across the platen toward thenozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described by way of exampleonly with reference to the appended drawings wherein:

FIG. 1 is a perspective view of a girth weld coating machine;

FIG. 2 is a side elevation of FIG. 1;

FIG. 3 is a plan view of FIG. 1;

FIG. 4 is an end of the machine of FIG. 1;

FIG. 5 is a perspective view of a support frame incorporated in to themachine of FIG. 1 with a portion removed for clarity;

FIG. 6 is a perspective view of an application head used on the machineof FIG. 1;

FIG. 7 is a rear perspective of the application head of FIG. 6;

FIG. 8 is a plan view of the application head of FIG. 6;

FIG. 9 is an end view of the application head of FIG. 6;

FIG. 10 is an enlarged view of a portion of FIG. 9 with in the chaindotted circle G;

FIG. 11 is a perspective view of an applicator sub assembly used in theapplication head of FIG. 6;

FIG. 12 is a plan view of the sub assembly of FIG. 11;

FIG. 13 is an end view of the sub assembly of FIG. 11;

FIG. 14 is a section on the line XIV-XIV of FIG. 12;

FIG. 15 is a section on the line XV-XV of FIG. 13;

FIG. 16 is an enlarged view of the circled area C of FIG. 15;

FIG. 17 is a front perspective of a dispensing unit incorporated in tothe applicator subassembly;

FIG. 18 is a front elevation of the dispensing unit of FIG. 17;

FIG. 19 is a perspective view of a reservoir used in the dispensing unitof FIG. 17;

FIG. 20 is a perspective view of a a dispensing unit incorporating thereservoir of FIG. 19; and

FIG. 21 is a section on the line XXI-XXI of FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

Referring therefore to FIGS. 1 to 4, a pipeline P is formed from pipesections S1, S2 welded to one another at a girth weld G. A girth weldcoating machine 10 is supported on the pipeline P and is used to apply acoating to the weld G, as will be described below.

The girth weld coating machine 10 includes a support frame 12 thatcarries an application head 14. As seen in FIGS. 2 and 3, the supportframe 12 has a pair of yokes 16, 18, that extend about the pipe P andare connected by stringers 20 to form a unitary cage structure 22 thatextends about the pipe P. A pair of wheels 24 are mounted on each of thestringers 20 so as to be spaced along the axis of the pipeline P. Thewheels 24 support the cage 22 and allow it to be moved along thepipeline P between locations of the welds G.

The yokes 16, 18 are semi-circular and have an inverted C configurationto allow the cage 22 to be lowered on to the pipeline P. The leadingyoke 16 has a pair of arms 26 (FIG. 4) pivotally connected to the yoke16 by a pin 28. Each arm 26 has a wheel 30 at its lower end and alocking pin 32 secures the arm 26 to the yoke 16 so the wheel 30 engagesthe underside of the pipeline P.

The trailing yoke 18 similarly has a pair of arms 34 pivoted to the yoke18 on opposite sides of the pipeline P and lockable in position by alocking pin 35 (FIG. 3). The arms 26, 34 are connected by stringers 35for conjoint movement. The yoke 18 and arms 34 carry a segmented supportring 36 that is cantilevered from the yoke 18 and arms 34 by pins 38(FIG. 5). The ring 36 extends radially outwardly to present a continuoussupport race 40 for the application head as will be explained more fullybelow.

A gantry 42 has a pair of side plates 44 that are connected to the yokes16, 18 and extend rearwardly along the pipe P. Cross members 46 connectthe side plates 44 which are relieved to form a bight to accommodate theapplication head 14. The distal end 48 of the plates 44 extends radiallyinwardly and carries a foot 49 that is adjustable radially to engage thesurface of the pipeline P. A pair of wheels 50 is mounted on the distalend 48 to carry the application head 14, as will be described below.

The application head 14, as best seen in FIGS. 6 and 7 has a cylindricalframework 59 provided by a pair of rings 60, 62 that are interconnectedby struts 64 to maintain the rings 60, 62 in spaced relationship. Eachof the rings 60, 62 is divided in to three segments 66, 68, 70, with thesegments 66 and 68 and 68 and 70 connected by hinges 72 (FIG. 7). Alatch assembly 74 releasably secures the segment 68 to segment 70 sothat the rings 60, 62 can swing open to allow the application head 14 topass over a pipeline P.

A platform 76 extends between a pair of struts 64 connecting thesegments 66. As shown in FIG. 8, a pair of rails 78 is located atopposite sides of the platform 76 to extend parallel to the rings 60,62. A cross beam 80 is supported on the rails 78 through guide blocks 82so it can slide along the rails 78 under the control of a linearactuator 84. The actuator 84 is mounted on the trunnions 86 on theplatform 76 and is connected to one end of the cross beam 80.

The cross beam 80 carries a U shaped retainer 88 with projecting ears89. The ears 89 are resilient and carry a dispensing roller 90 that isrotatable about an axis perpendicular to the rails 78. A clamp bar 92 ispositioned behind the cross beam 80 and can be moved toward or away fromthe platform 76 by an over-centre toggle 94.

The platform 76 is formed with an enlarged opening 100 at the oppositeend to the roller 90 to accommodate a nozzle sub assembly 102, best seenin FIGS. 9 to 14. The nozzle sub assembly 102 has a generally E-shapedframe member 104 with a central bar 106 a extending between a pair ofside bars 106 b, and an intermediate bar 106 c. A universal joint 108 issecured to the intermediate bar 106 c to allow movement about a pair oforthogonal axes and has a trunnion block 110 supporting a rod 112 forrotation about an axis parallel to the rails 78. The rod 112 has atransverse bore 114 at the opposite end to the trunnion block 110 and isreceived between a pair of ears 116 located on a strut 64 (FIG. 6). Apin 118 secures the rod 112 to the ears 116 to permit movement about anaxis perpendicular to the rails 78.

A load cell 120 is mounted on the frame member 104 at the intersectionof the central bar 106 a and intermediate bar 106 c and has a loadtransfer rod 122 (FIG. 10) extending to an electric linear actuator 124.The actuator 124 is pivotally connected to a clevis 126 on a strut 64with a control incorporated in to the actuator 124 to regulate movementof the actuator 124.

Referring again to FIGS. 11 to 16, a motor 130 is mounted on theunderside of the frame member 104 between the intermediate bar 106 c andone of the side bars 106 b. The motor 130 drives a toothed drive belt132 through a pulley 134. The belt 132 extends below one of the sidebars 106 b and is entrained about a driven pulley 136 mounted on adriven axle 138. The driven axle 138 is rotatably supported in bearings140 carried on lugs 142 projecting from the underside of the framemember 104 at the intersection of the side bars 106 b and the centralbar 106 a. The driven axle 138 projects inwardly from the lugs 142 andis formed with a square section drive shaft 144.

The drive shaft 144 operatively engages with a dispensing unit 150 thatis supported on the frame member 104. Referring to FIGS. 17-21, thedispensing unit 150 has an elongate body 152 with a cavity 154 toreceive a nozzle, as will be described below. As best seen in FIG. 21, aslit 155 extends through the base of the cavity 154 and opens in to apart cylindrical cavity defined by a roof 157 that extends to eitherside of the slit 155 and curved shroud 156 that depends from either sideof the body 152. The roof 157 slopes away from the slit 155 and thelower edge 159 of the shroud 156 is turned over to provide a wipingsurface. T-shaped mounting blocks 158 are formed at opposite ends of thebody 152 and are received in notched supports 160 (FIG. 11) on the uppersurface of the sidebars 106 b. The blocks 158 are retained by lockingpins 162 that pass through aligned bores 164.

Mounting legs 166 depend from the distal ends of the body 152 and carryroller supports 168. The supports 168 are rotatable in the legs 166 andhave inwardly directed bosses 170, best seen in FIG. 16. One of thebosses 170 extends through the leg 166 and is formed with a clutch 172.The clutch 172 has an open jaw 174 that is dimensioned to receive thedrive shaft 144.

A roller 176 is located on the bosses 170 within the cavity 157. Theroller 176 is a conventional paint type roller with a hollow core thatis a friction fit on the bosses 170. The roller 176 has an outerapplication surface that is selected to be compatible with the coatingmaterial to be applied. Typically, the roller 176 has a foam body, butdifferent materials may be used. The roof 157 is located closer to theaxis of rotation of the bosses 170 than the free body dimension of theroller 176 so that the roller is compressed by the roof when it ismounted on the bosses. In a typical application with a foam roller, theroller outside diameter is 2⅜ inch. so the radius of the sponge rolleris 1.1875 inch, and the radius of the extrusion housing is 1.030 inch.The compression between extrusion housing and sponge roller is:1.1875−1.030=0.157 inch interference which provides a compression ofbetween 40% and 45% of the free body dimension. This has provedsatisfactory for a typical coating, although this may vary if differentmaterials are used for the roller and coating.

The material to be applied to the pipe P is held in a reservoir 200shown in FIG. 19. The reservoir 200 has a flexible plastic pouch 202which is open at one end. The opposite end of the pouch 202 is stretchedaround a nozzle 204 which is held in place by tension in the material ofthe pouch 202. If required, the nozzle 204 may be secured to theopposite end of the pouch 202 by adhesive, welding or integrally moldingthe pouch and nozzle, but it has been found that the friction fit isusually sufficient. The nozzle 204 is of complimentary shape to thecavity 154 formed in the holder 150 and has a continuous elongate slot206 to allow the coating material to be dispensed through the slit 155in the body 150. Bridges 208 are disposed along the slot to maintain thespacing and project upwardly from the nozzle 204 to maintain spacing ofthe walls of the pouch 202. The nozzle 204 is tapered in cross sectionso as to be a snug fit within the cavity 154, where it is held by keeperplates 210.

Referring again to FIGS. 6 and 7, power for the actuators 84, 124 andmotor 130 is provided from a rechargeable power pack 220 carried on oneof the struts 64 that extends between the segments 68. A counterweight222 is also mounted on the strut 64 to offset the mass of the platform76 and nozzle sub assembly 102. A control box 224 is mounted on theapplication head 14 to contain the controllers for the actuators 84, 124and motor 130.

As shown in FIGS. 1 to 4, the application head 14 is rotatably supportedon the gantry 42 within the bight provided by the side plates 44 byrings 60, 62. The inner edge of ring 62 is supported by the wheels 50carried on the distal end 48 of the side plates 44.

The ring 60 has a series of wheels 180 uniformly spaced about thecircumference. The wheels 180 are supported on the race 40 of the ring36 so that the application head 14 is free to rotate about the axis ofthe pipe P on the wheels 50, 180.

The radially inner edge of the ring 60 is formed with gear teeth 182that mesh with a drive sprocket 184 (FIGS. 2 and 3). The sprocket 184 isdriven by a drive shaft 186 connected to a motor 188 that is locatedbetween the side plates 44. A pair of idler sprockets 185 are located onthe distal end of arms 34 to locate and stabilise the ring 60. Operationof the motor 188 rotates the drive shaft 186 and causes the applicationhead 14 to rotate relative to the support frame 12 about the pipe P.

In use, the support frame 12 is positioned on the pipe P by opening therings 60, 62 and the arms 26, 34 so the machine can be lowered on to thepipe P. The rings 60, 62 and arms are closed and the machine moved alongthe pipe P on the wheels 24 until the application head 14 is centredover the girth weld G. The foot 49 is brought in to engagement with thepipe P to stabilise the gantry 42 with the application head 14concentric to the pipe P.

As shown in FIG. 20, the dispensing unit 150 is formed as a disposableunit incorporating the reservoir 200, body 152 and roller 176. Thereservoir 200 is loaded with premixed coating material through the openend of pouch 202, which is then folded over several times to seal thepouch 202. The body 152 is secured to the frame member 104 by locatingthe T shaped mounting blocks 158 in to the notched supports 160 wherethey are secured by the pins 162. As the body 152 is secured, the jaw174 of clutch 172 is aligned with and engages the drive shaft 144 toestablish a drive to the roller 176.

The distended pouch 202 of reservoir 200 is laid on to the platform 76,shown in ghosted lines in FIG. 21. The opposite end of the pouch 202 isheld in position by the clamp bar 92 and the roller 90 (also shown inghosted outline) snapped in to position between the ears 89. At thistime, the actuator 124 is retracted so that the nozzle sub assembly 102is held away from the pipe P.

The motor 188 is operated and the drive is transmitted through thesprocket 184 so that the application head 14 rotates about the pipe P.The control 174 initiates operation of the motor 130 so that the roller176 is driven in the same direction of rotation as the application head14 about the pipe P.

Actuator 124 is operated to lower nozzle sub assembly 102 until theroller 176 is in to contact with the pipe P with a radial forcedetermined by the load cell 120. The linear actuator 84 is operated tomove the cross beam 80 progressively along the rails 78. The movement ofthe cross beam 80 causes the roller 90 to displace the coating materialfrom within the reservoir 200 and move it through the nozzle 204 and onto the roller 176. The efflux of material from the slit 155 causes afurther localised compression of the roller 176 as it passes beneath theslot 155 so that the coating material is loaded on to the roller. As theroller 176 moves across the surface of the pipe P, it spreads thematerial to apply a uniform coating to the surface over the girth weldG. During rotation of the head 14, the universal joint 108 accommodatesirregularities in the pipe P to maintain consistent contact between theroller 144 and the pipe P.

Load cell 120 monitors the radial force applied through the frame 104 tothe roller 176 and modulates the force to maintain a predeterminedprofile. In practical testing, it has been found that a constant forceprovides satisfactory results so that as the thickness of the coatingincreases, the actuator 124 moves the roller 175 radially outward.Alternatively, the force may be progressively decreased as the coatingis applied as determined by the number of rotations of the applicator14, and maintained at a constant value once all the coating material hasbeen dispensed. However, a constant force that accommodates theincreasing thickness of the coating whilst ensuring uniform applicationof the coating has been found satisfactory for most applications.

Rotation of the application head 14 continues until all the coatingmaterial is displaced from the reservoir 200. The linear actuators 84are disabled once the roller 90 has reached the limit of its travel,indicating all the material is dispensed. Once the coating material isdispensed, the applicator head 14 may continue for several rotationsafter the material is dispensed to ensure a uniform coating. At thattime, the actuator 124 lifts the roller 176 away from the surface of thepipe P with the motor 130 continuing to rotate the roller 176 as it islifted to maintain a smooth surface.

With the coating applied, drive to the applicator head 14 and roller 176is terminated and the foot 49 is retracted. The machine 10 may then bemoved along the pipe to the next location. The spent dispensing unit 150including the reservoir 200 is removed from the frame member 104 fordisposal by releasing the pins 162 and lifting the mounting blocks 158and releasing the clamp bar 92. A new dispensing unit 150 includingroller 176 and a reservoir 200 may then be deployed and the subsequentgirth weld coated. The components that come in to contact with thecoating may therefore be disposed of after each weld is coated, therebyavoiding the need for continuous operation or clean up between coatingoperations.

The provision of the disposable reservoir 200 allows coating material tobe premixed under controlled conditions and fora measured volume to bedispensed to ensure a proper application. The coating material may bevaried to suit particular applications without the need to clean themachine components with solvents and the like. The control of the radialforce by the load cell also allows the quality of the coating to bemaintained and the load profile adjusted as different conditions aremet.

It will be seen therefor that the girth weld coating machine is able toapply a coating material in a controlled and uniform manner and by usingdisposable reservoir and roller, the use of solvents betweenapplications is mitigated.

Although the invention has been described with reference to certainspecific embodiments, various modifications thereof will be apparent tothose skilled in the art without departing from the spirit and scope ofthe invention as outlined in the claims appended hereto. The entiredisclosures of all references recited above are incorporated herein byreference.

What is claimed is:
 1. A girth weld coating machine comprising a supportstructure to mount said girth weld coating machine to a pipe and anapplication head carried by said support structure to be rotatablerelative thereto and encompassing said pipe to apply a coating materialto the surface of the pipe, said application head including a pair ofrings spaced apart along said pipe, a platform extending between andsecured to said rings so as to be spaced from and rotatable about saidpipe and a dispensing unit carried by said platform and operable todispense a coating material on to said surface of said pipe as saidplatform rotates about said pipe, each of said rings being rotatablysupported on said support for continuous rotation about said pipe tomove said platform and said dispensing unit about said pipe.
 2. Thegirth weld coating machine of claim 1 wherein said support structureincludes a pair of yokes to encompass said pipe and secure said girthweld coating machine on said pipe, each of said yokes having a pair ofarms pivotally connected to opposite ends of said yoke to extend aboutsaid pipe.
 3. The girth weld coating machine of claim 2 wherein saidsupport structure has a plurality of wheels to engage the surface ofsaid pipe and permit displacement along the pipe.
 4. The girth weldcoating machine of claim 1 wherein said support structure includes agantry extending along the axis of said pipe and said application headis supported by said gantry.
 5. The girth weld coating machine of claim4 wherein said gantry has sets of wheels at spaced locations along thepipe, said wheels of each set being disposed about the circumference ofthe pipe to support respective ones of said rings for rotation aboutsaid pipe.
 6. The girth weld coating machine of claim 5 wherein a drivemember extends from said support structure to engage a driven member onone of said rings to induce rotation about said pipe.
 7. The girth weldcoating machine of claim 6 wherein said drive member is a pinion andsaid driven member is a ring gear.
 8. The girth weld coating machine ofclaim 1 wherein said dispensing unit includes a reservoir mounted onsaid platform and an applicator mounted on a subassembly, saidsubassembly being dispaceable radially relative to said rings.
 9. Thegirth weld coating machine of claim 8 wherein a motor is operablebetween said subassembly and a framework of said application head toeffect radial displacement.
 10. The girth weld coating machine of claim9 wherein said subassembly is mounted for movement about orthogonal axesrelative to said framework.
 11. The girth weld coating machine of claim9 wherein radial displacement of said subassembly is modulated todetermine the radial force exerted by said applicator on said pipe. 12.The girth weld coating machine of claim 11 wherein radial displacementof said subassembly is modulated to maintain the radial force constantas coating is applied to said pipe.
 13. The girth weld coating machineof claim 12 wherein a load cell is interposed between said motor andsaid subassembly to monitor radial force.
 14. The girth weld coatingmachine of claim 1 wherein each of said rings is segmented and moveablebetween an open position where said rings can pass around said pipe anda closed position in which said rings encompass said pipe.
 15. The girthweld coating machine of claim 14 wherein said rings are connected bystruts to provide a cylindrical framework.
 16. The girth weld coatingmachine of claim 15 wherein said platform extends between a pair of saidstruts.
 17. The girth weld coating machine of claim 16 wherein asubassembly is pivotally mounted to said framework for radialdisplacement relative to said pipe.
 18. The girth weld coating machineof claim 16 wherein said dispensing unit includes a reservoir of coatingmaterial supported on said platform and an applicator mounted on saidsubassembly.
 19. The girth weld coating machine of claim 18 wherein adispenser is mounted on said platform to expel coating material fromsaid reservoir.
 20. The girth weld coating machine of claim 19 whereinsaid reservoir is a bag and said dispenser is a roller moveable acrosssaid platform.
 21. The girth weld coating machine of claim 20 wherein apair of actuators are located on opposite sides of said platform to movesaid roller across said bag.
 22. The girth weld coating machine of claim20 wherein said bag is connected to an elongate nozzle in saidapplicator.
 23. The girth weld coating machine of claim 22 wherein saidapplicator includes a roller and said nozzle dispenses coating materialon to said roller for transfer on to said pipe.
 24. The girth weldcoating machine of claim 23 wherein said roller is displaceable radiallyrelative to said rings.
 25. The girth weld coating machine of claim 23wherein said roller is driven as coating material is dispensed.
 26. Thegirth weld coating machine of claim 25 wherein a motor is mounted onsaid subassembly to drive said roller.
 27. The girth weld coatingmachine of claim 23 wherein a shroud extends partially about saidroller.
 28. The girth weld coating machine of claim 27 wherein saidshroud compresses said roller.
 29. The girth weld coating machine ofclaim 23 wherein said dispensing unit including said roller and said bagis separable from said application head.